1. Field of the Invention
The present invention relates, generally, to attachments for loader vehicles. More particularly, the invention relates to a grading attachment for a small loader vehicle, such as a BOBCAT or similar loader.
2. Background Information
Loaders, also known as skid steer loaders, are compact equipment widely owned by companies in the construction and other industries. Such loaders may be either wheeled or track vehicles. The movement of the loader is usually controlled by left and right control handles. Forward and reverse movement of the left and right control handles controls the forward and reverse speed of the left and right wheels, respectively.
As an example, if the left control handle is moved forward farther than the right control handle, more power is provided to the left wheels or track than to the right wheels or track, and the loader will turn to the right. If the left control handle is moved forward and the right control handle is moved back, the wheels or tracks on opposite sides of the loader will rotate in opposite directions, the loader may turn about its vertical axis. Of course, as the wheels are not steered to make such turns, some skidding of the wheels results as the loader is turned.
The state of the art includes various graders and grader attachments for vehicles.
U.S. Pat. No. 5,529,131 to Van Ornum discloses a grading attachment for a loader having a pair of wheels at its front, and a hydraulically actuated blade that pivots about a vertical axis. Since the blade is rotated by means of hydraulic cylinder connected to a mounting plate, the blade cannot rotate all the way around to grade in reverse.
U.S. Pat. No. 4,635,730 to Larsson discloses a hydraulically actuated blade control mechanism which allows the blade to swing transversely and pivot, but again, because of hydraulic linkages it does not appear that the blade could rotate completely around to be able to grade in reverse.
Both of these attachments have front wheels to support their weight, but those wheels are not steerable. Steering of the Van Ornum and Larsson grading attachments is accomplished through the steering of the loader, which is done by the loader's traction wheels. With the extended length of the grading attachment, such steering typically requires greater torque on the traction wheels. It is likely that there will be slippage between the traction wheels and the newly graded surface over which they are operating, thereby tearing up the newly graded surface.
U.S. Pat. No. 6,168,348 to Meyer et al. also discloses a surface leveling system that can be attached to a loader, and it too has non-steerable front wheels.
U.S. Pat. No. 5,775,438 to Confoey et al. discloses a scraping device for attaching to a loader, but it has no front wheels to support it.
U.S. Pat. No. 3,598,186 to Coontz discloses a grading blade for attachment to a tractor that has a hydraulically-actuated blade rotation mechanism, but the device hangs off of the back of a tractor and has no supporting wheels.
Steerable wheels are found on conventional graders such as those disclosed in U.S. Pat. No. 4,081,033 to Bulger et al. and U.S. Pat. No. 3,486,564 to Page et al., but those wheels are steered mechanically, and such mechanical arrangements are not suited for a device to be attached to a loader.